Saturday 5 May 2012 09.18 EDT
First published on Saturday 5 May 2012 09.18 EDT

It was started by a handful of isolated enthusiasts, gradually became a cult craze, and is now threatening to become a commercial enterprise.

Spoof reviews posted on Amazon have sent demand for the most unlikely merchandise soaring and are playing havoc with the online giant's famed algorithms, the complex formulas that recommend what else buyers of a particular product may be interested in purchasing.

The current must-have item heavily lauded by the spoof reviewers is a £50 canvas print of the TV presenter Paul Ross. Mugs with the same image costing a more modest £8.99 are selling well, with Amazon suggesting that customers also buy a particular bottle of methylated spirit attracting the sort of reviews normally associated with Château Latour.

So far 471 people have enthusiastically reviewed the Paul Ross print, with one explaining: "I've ordered four of these now: one of them is above the fireplace and is naturally the pride of our entire home. On the second canvas I've cut out the section where Paul's face is, and when I drive to pick up the kids I wear the canvas and pretend that I'm a famous celebrity dad, the kids simply love it."

Many of the reviews are unprintable, displaying a scatological humour of the sort long championed by cult comic Viz. But others clearly harbour aspirations to make an appearance in Private Eye's "Pseuds' Corner".

One reviewer of the Ross print purrs: "On first encountering this seminal artwork, one is reminded of the great depictions of the Christ in Renaissance paintings. The subject's gaze – warm, but penetrating; wise, but honest – harks back to such works as Caravaggio's Supper at Emmaus."

Also popular is a print jigsaw of Manchester United's former finance director Nick Humby, currently selling on Amazon for £15.99.

"It simply doesn't matter how bad a day you may be having – knowing you have the Humby jigsaw to come home to just makes everything better," explains one reviewer.

The Ross and Humby prints and mugs are sold by Media Storehouse, which turns more than 2m images, culled from several major photo libraries, into merchandise.

"Some of the reviews could have been written by professionals; they're really very funny," said Matt Hamer, the company's director, who became aware of how the spoof review trend was creating a market for unlikely products about three years ago. In the beginning there were a few hundred reviews driving demand, but Hamer says there are now thousands.

"People are trying to outdo each other," he said. "Quite a lot is bought by students. It came completely out of the blue; there was no reason why the images should have been picked up. There was a picture of Su Pollard with a Kiss Me Quick hat which was popular for a while, but Paul Ross has been by far and away the biggest success."

Demand for the bizarre merchandise is the culmination of a trend that started almost a decade ago when a handful of spoofers targeted some unlikely products. A 75-metre roll of tinfoil has garnered 223 enthusiastic reviews and has become something of a cult forum. A typical reviewer extols the product as "sensational", explaining: "When you roll it out of the box it creates a smooth, silky feeling across my skin."

Many participants are inspired by one of the original spoof reviewers, Henry Raddick, who achieved near-celebrity status for his antics. Reviewing The English Cocker Spaniel Handbook, Raddick, who had a spaniel, Barry, enthused: "I enjoyed the book immensely and, though I have a sneaking suspicion that Barry is using the book as porn, I wholeheartedly recommend it."

One of Raddick's most enthusiastic devotees is Wayne Redhart, a piano teacher and musician whose often absurd reviews reveal an anarchic wit. Redhart (not his real name) told the Observer that he started posting because he didn't "have the cast-iron balls to attempt standup".

"I can't think of any other medium that might have led me to make any serious effort with amateur comedy, even as a writer," Redhart said. "On Amazon, you're basically guaranteed some sort of ready (if frequently unwilling) audience upon which to foist your material."

Redhart's reviews on Amazon, which declined to comment, earned him a following via a Facebook group that rapidly grew in popularity. "A smallish crowd of people gave me rather a lot of helpful votes which propelled me up the rankings pretty fast," he said. "Trying to work up more and more places was a huge part of spurring me on."

While conceding it would be "a shame if Amazon were flooded with too many attempts to be funny", Redhart said he hoped his actions offered a warning to potential buyers. "Amazon is flooded with low-key books that have three -star reviews. I hope it actually reminds them to be wary of putting too much trust in reviews."